Solid and liquid food substances are usually stored in food-grade liquid-tight containers typically made of plastic materials. The container may be a functional package such as a single-use capsule for preparing a beverage or a cartridge for feeding a beverage production machine with soluble coffee powder or coffee mixes. The package may be a beverage cup for simply holding a beverage or may also be food container for shortenings and the like. All these food and beverage packages are designed to store or simply hold the ingredients or beverage in a liquid-tight environment. Most of the existing packages are over-dimensioned and/or use too much packaging material. In particular, their rigidity-to-weight ratio is not optimized. Therefore, their imprint on environment can be drastically reduced by optimizing this ratio.
Moreover, certain food substances can lose their particular characteristics due to loss of gases or aroma, e.g. carbonated drinks or coffee powder, or need to be kept dry and inaccessible to oxygen and moisture to maintain freshness, e.g. coffee or milk powder. Accordingly, packaging containers with gas barrier properties can be desirable for enabling a long shelf life of the enclosed food substance.
It is known from the prior art to form a mono- or multilayered packaging container for providing a rigid and liquid-tight, eventually gas-tight, container body. Such a container body can then be hermetically sealed for example by means of a dedicated cover member.
It exists also entirely flexible packaging which offer possible alternatives to rigid packaging. One drawback of a flexible container is that it requires an external support for holding liquids in particular hot liquids and/or liquids under pressure. For instance, a flexible beverage capsule requires to be placed in a capsule holder supporting the faces of the capsule in order to avoid the walls to tear apart or burst under the pressure of liquid in the capsule.
In general, these containers are formed by thermoforming, blow moulding or injection moulding of multilayered plastic material. Usually, the plastic material consists of a polypropylene, polyethylene, and/or PET layer for obtaining a rigid container body. For obtaining gas-barrier properties, a secondary layer of plastic material such as of for example ethylene-vinyl-alcohol-copolymer (EVOH), polyamide or metallic material such as aluminium may be present.
However, the above outlined mono- or multilayered design of packaging containers suffers several drawbacks such as its relatively high weight, high manufacturing costs and poor recycling properties.
Moreover, it is known to provide a main body of a packaging container with in-mould labels having oxygen barrier properties.
Thereby, in-mould labelling (IML), which is a label moulding technique used in blow moulded, injection moulded and thermoformed containers, have in general an inner layer compatible with the plastic material which partially melts to bond to the formed plastic structure.
In general, the label is placed in the mould wherein it is held in place by vacuum or other dedicated positioning means. The mould is then closed and molten plastic resin is poured or injected into the mould in order to form the packaging container. Thereby, the adhesive of the label is activated due to the heat resulting from the injection of hot resin and thus, the label is adhered to the container, i.e. the label becomes moulded to the container wall.
EP 1440903 refers to a cartridge for the preparation of a beverage with a barrier coating applied by a number of mechanisms including in-mould labelling.
JP 10129737 A for example relates to a packaging container with an opening having oxygen gas barrier properties. Thereby, an inner wall of a side face of a bottomed container main body and an inner wall of a bottom thereof is provided with in-mould labels for improving the oxygen gas barrier properties of the packaging container.
Furthermore, GB 1348370 discloses a container comprising a structure or frame, made of a rigid or semi rigid material, which is used as a support for applying a softer material, like for instance a film by an in-mould labelling technique so as to obtain a container
FR 2700493 A is a French patent application that also discloses a container that is made by injecting a rigid frame onto which a label is attached to complete the container body, for instance by in-mould labelling.
In the field of containers used for food preparation, and in particular in the case of capsules used for the preparation of beverages or the like, in food preparation machines, for instance in coffee machines of the espresso type, capsules are subject to high mechanical forces, due to the temperature of the dissolution or extraction fluid which is injected inside the capsule to extract and/or dissolve the ingredient contained therein and produce a beverage. Another source of mechanical tension exerted onto the capsule is the high pressure of the fluid that is injected into the capsule to realize a proper extraction of the capsule contents. This is particularly true in the case of espresso type beverages, wherein the roast and ground coffee powder that is contained inside the capsule requires a high pressure of injection fluid (e.g. water) to form a quality beverage. Temperatures of the injected fluid can amount up to 70° C., or even about 80° C. to 85° C., and the pressure of the injected fluid inside the capsule can reach 6 to 8 bars, or even 8 to 12 bars. In some particular cases, the pressure inside the capsule during the extraction process can reach pressures higher than 12 bars, for instance comprised between 10 and 20 bars.
It is therefore particularly important that the structure of the capsule be without defect, especially concerning the shape of the capsule, as it must be precisely inserted and positioned inside the extraction chamber of the beverage preparation machine. If the capsule presents structural defects or deformations, there is a risk that the capsule is not properly maintained inside the extraction chamber of the machine, and leakage can appear, or the capsule can even be damaged during the pressure build-up.
Typically, capsule-like containers for use in beverage preparation machines which are known in the art comprise a rigid or semi-rigid structure with a lower side which is preferably disc-shaped, at least one, but preferably at least two and even more preferably at least three substantially vertical pillars extending from the lower side, the said pillars being linked to a top circular frame, which defines the surroundings of the capsule top side. A label is usually attached between the lower side and the upper circular frame, as an envelope, thus defining the capsule side walls. The label is also bound to the pillars, which support it and reinforce the label against laterally directed forces that may apply on the capsule.
Importantly, in order to allow proper closing of the capsule, the circular top frame comprises a L-shaped cross-section, with one circular portion disposed vertically, to which the pillars are linked, the vertical portion being linked at its upper side to a horizontal circular edge of the capsule, onto which a horizontal top wall, for instance a flexible closing film, can be attached (e.g. heat sealed) in order to close the capsule after its filling.
It was found by the applicant that with the in-mould labelled containers and manufacturing methods for making in-mould labelled containers known in the art, the upper portion of the rigid structure can present defects, particularly when the said structure comprises at least three pillars disposed at an equal distance from one another across the periphery of said structure, and when the structure comprises a lower side which is closed except for a central dispensing opening. In this case, the injection point for moulding the structure is off-centred, so that it is not at an equal distance from the pillars.
So far, no appropriate solution was found in such cases, and the known in-mould labelled containers of the art present defects which can be particularly negative and even dangerous when the container is a capsule for use in a beverage preparation machine that injects a fluid under pressure in the said capsule. In such instances, due to the pressure build-up, the zones of the capsule which present defects can be damaged so that leakage will appear in the machine. In some cases, this will lead to poor quality of the final product as a certain quantity of the fluid that is supposed to extract or dissolve the capsule contents, will leak outside. In some more serious cases though, the leakage of fluid under pressure can lead to splashes outside of the beverage preparation machine, onto the consumer, which is of course particularly undesirable, especially when the said fluid is hot.
Such damages to the capsule have been analyzed by the applicant, who found that this is due to delamination of the label in zones of the capsule where the rigid structure does not have sufficient material. This creates grooves or creases in the surface of the structure, or wrinkles in the surface of the label. Such imperfections in the structure and/or surface of the label lead to leakage when pressure inside the capsule builds up.
It is an objective of the present invention to overcome the above imperfections to known in-mould labelled containers.